我们用8085汇编语言编写一个程序，以实现十进制递减计数器（从99到00）。该程序必须在以下条件下运行。
我们向累加器加载99。
在累加器中显示累加器中的计数值。RST5.5处于未屏蔽状态，并且中断系统被启用。
该程序如下：
FILE NAME DOWNCNTR.ASM ORG C000H CURDT: EQU FFF9H UPDDT: EQU 06D3H RDKBD: EQU 0634H MVI A, 99H ; Initialize A with 99. REP: STA CURDT ; Store A value in CURDT. CALL UPDDT ; Display contents of CURDT in data field. MVI A, 00001110B SIM ; Unmask RST5.5 EI ; Enable Interrupt system CALL RDKBD ; Wait till a key is pressed and load ; the key code in Accumulator, but ignore it. LDA CURDT ; Reload A from location CURDT. ADI 99H DAA ; Decrement A in decimal notation by ; adding 99, which is 10's complement of 01. JMP REP ; Jump to REP to display the next count.